liz, syria has one of the largest armies in the middle east. why hasn't the dictatorship been able to put down the rebellion? >> reporter: well, for a start, they're fighting on dozens of fronts and up and down the country. but secondly, this not terribly well trained army is fighting a very nimble mobile insurgency and that is the most difficult kind of warfare. >> pelley: the war has been encroaching on the capital where you are now over the last several months. what's the fighting been like there today? >> reporter: inside the city, hit-and-run attacks, sporadic gunfire. but in the suburbs really heavy shelling. the heaviest we've seen so far from the air from fighter planes and also mortars and tank shells. in fact, until just a few minutes ago the windows were rattling here in the hotel. >> pelley: no end in sight. liz, thanks very much. scientists studying climate change are warning of a new source of greenhouse gases warming the earth. and who is buying the illegal tusks of slaughtered elephants? our hidden camera investigation coming up